[Dissertations 25 years after date 25. Dentures: a question of grinning and bearing it]. / Proefschriften 25 jaar na dato 25. Een kunstgebit, een kwestie van doorbijten.

'Dentures: A question of grinning and bearing it' is not just the title of a 25-year-old thesis, but it also reflects the content well. Dissatisfaction with complete dentures is not only determined by the quality of the dentures and the oral conditions, but also and just as much by the patient's capacity to adapt to and accept the dentures. In order to treat an edentulous patient adequately, an oral healthcare provider should pay special attention to these aspects. After 25 years of further scientific study, this conclusion is still true. The current care standard for edentulous patients with atrophy of the residual mandibular alveolar ridge is an overdenture supported by 2 implants. For edentulous patients with a solid residual mandibular alveolar ridge, conventional complete dentures are the first choice of treatment. Only in cases of obvious remaining complaints, should an implant-supported overdenture be considered.

[Neutral zone. An anatomic space which is often neglected while fabricating removable complete dentures]. / Neutrale zone. Een bij vervaardiging van volledige gebitsprothesen vaak vervaarloosde anatomische ruimte.

When designing complete dentures, consideration should not only be given to the occlusal concept but also to the occlusal system as a whole. An important part of that system is the position of the artificial teeth. This prosthetic part of the occlusal system is directly related to the tongue, the floor of the mouth, the cheeks and the lips. The artificial teeth of the mandibular dentures have to be positioned in the so-called 'neutral zone' of the edentulous mandible. The neutral zone is the stress-free area between the tongue on one side and, on the other side, the mimic muscles, which are responsible for the movement of the lips and cheeks. Moreover, the maxillary posterior artificial teeth and the supporting acrylic surfaces of the maxillary denture have an important function in providing support for the upper lip and cheeks in order to prevent a 'denture look' appearance.

[Indications for removable partial dentures]. / De indicaties voor een partiële gebitsprothese.

Since there are many ways of preserving a natural dentition, if necessary with support of solitary crowns and fixed partial dentures, sometimes on dental implants, removable partial dentures are nowadays primarily indicated in patients with complaints about missing teeth in the aesthetic zone, which cannot be solved in another way. In addition to this, a removable partial denture is indicated in patients with extremely reduced dentitions or large or multiple edentulous areas, in patients with severe periodontitis or excessive loss of alveolar bone, in patients who are physically or emotionally vulnerable, as an interim solution on the way to edentulousness, as a temporary solution waiting for more extensive treatment and for patients who cannot afford an alternative.

An eight-year follow-up to a randomized clinical trial of aftercare and cost-analysis with three types of mandibular implant-retained overdentures.

Mandibular implant overdentures increase satisfaction and the quality of life of edentulous individuals. Long-term aftercare and costs may depend on the type of overdentures. One hundred and ten individuals received one of 3 types of implant-retained overdentures, randomly assigned, and were evaluated with respect to aftercare and costs. The follow-up time was 8 years, with only seven drop-outs. No significant differences (Kruskal-Wallis test) were observed for direct costs of aftercare (p = 0.94). The initial costs constituted 75% of the total costs and were significantly higher in the group with a bar on 4 implants, compared with the group with a bar on 2 implants and the group with ball attachments on 2 implants (p = 0.018). The last group needed a significantly higher number of prosthodontist-patient aftercare contacts, mostly for re-adjustment of the retentive system. It can be concluded that an overdenture with a bar on 2 implants might be the most efficient in the long term.

[Incorporation of implant overdentures into the dental curriculum]. / De invoering van de overkappings- prothese op implantaten in het reguliere onderwijsprogramma.

This article is focusing on incorporation of implant overdentures into the dental curriculum. For mandibular edentulism, an implant-retained overdenture should nowadays be considered a first choice for prosthodontic care, if not the standard of care. Yet, it is not incorporated in practical teaching today. Curriculum change is always difficult. The needs of our patients specifically, and those of society generally, should be primarily drivers of innovation of the curriculum. Therefore, Dutch dental schools should make sure that graduated students are experts in analyzing edentulous patients' problems, in considering possible treatments, and in carrying out the standard of care.

Transforming growth factor-beta1 incorporation in an alpha-tricalcium phosphate/dicalcium phosphate dihydrate/tetracalcium phosphate monoxide cement: release characteristics and physicochemical properties.

The osteoconductive properties of calcium phosphate cements (CPCs) may be improved by the addition of growth factors, such as recombinant human transforming growth factor-beta1 (rhTGF-beta1). Previously we have shown that rhTGF-beta1 was released from cement enriched with rhTGF-beta1 and subsequently stimulated the differentiation of pre-osteoblastic cells from adult rat long bones. It is unknown whether the addition of rhTGF-beta1 changes the material properties of this alpha-tricalcium-phosphate (alpha-TCP)/tetracalcium-phosphate-monoxide (TeCP)/dicalcium-phosphate-dihydrate (DCPD) cement, and what the characteristics of the release of rhTGF-beta1 from this CPC are. Therefore, in the present study we determined the release of rhTGF-beta1 from cement pellets in vitro. The possible intervening effects of the CPC modification for intermixing rhTGF-beta1 on physicochemical properties were studied by assessing the compressive strength and setting time, as well as crystallinity, calcium to phosphorus ratio, porosity and microscopic structure. Most of the previously incorporated rhTGF-beta1 in the cement pellets was released within the first 48 h. For all concentrations of rhTGF-beta1 intermixed (100 ng-2.5 mg/g CPC), approximately 0.5% of the amount of rhTGF-beta1 incorporated initially was released in the first 2 h, increasing to 1.0% after 48 h. The release of rhTGF-beta1 continued hereafter at a rate of about 0.1% up to 1 week, after which no additional release was found. The initial setting time, nor the final setting time was changed in control cement without rhTGF-beta1 (standard CPC) or in cement modified for rhTGF-beta1 (modified CPC) at 20 degrees C and 37 degrees C. Setting times were more than six times decreased at 37 degrees C compared to 20 degrees C. The compressive strength was initially low for both standard CPC and modified CPC, after which it increased between 24 h and 8 weeks. The compressive strength for the modified CPC was significantly higher compared with standard at 1, 2, and 8 weeks after mixing. X-ray diffraction revealed that both standard and modified CPC changed similarly from the original components into crystalline apatite. The calcium to phosphorus ratio as determined by an electron microprobe did not differ at all time points measured for standard CPC and modified CPC. In both standard CPC and modified CPC the separated particles became connected by crystals, forming a structure in which the particles could hardly be recognised in a densifying matrix with some small pores. The present study shows that the calcium phosphate cement is not severely changed by modification for the addition of rhTGF-beta1. The addition of rhTGF-beta1 in CPC enhances the biologic response as shown in our previous study and did not interfere with the aimed physical and chemical properties as shown in this study. We conclude that the addition of rhTGF-beta1 enlarges the potential of the CPC in bone replacement therapy.

Comminution of food with mandibular implant-retained overdentures.

When complete-denture wearers are treated with from four to six implants and mandibular implant-borne prostheses, masticatory performance improves. No significant improvement has been observed with two implants and implant-mucosa-borne overdentures, suggesting that the masticatory performance of edentulous subjects depends on the degree of support for their mandibular prostheses by implants or alveolar mucosa. To verify this hypothesis, we studied, in a randomized clinical trial, the comminution of an artificial test food during mastication. The trial involved the provision of a new maxillary denture and either a new conventional mandibular denture, a mandibular overdenture retained by two permucosal cylindric implants through a single bar-clip attachment, or a mandibular overdenture retained by a transmandibular implant through five clips on a triple-bar construction with cantilever extensions. In comparison with the subjects wearing mandibular implant-retained overdentures, the subjects with conventional complete dentures needed between 1.5 and 3.6 times more chewing strokes to achieve an equivalent reduction in particle size. No differences in masticatory performance and efficiency were found between the subjects who had received two permucosal cylindric implants and those who had received a transmandibular implant. The results suggest that the increased retention and stability of the mandibular denture, rather than the degree of support by implants or alveolar mucosa, determine the wearer's ability to comminute food during mastication.

A clinical evaluation of implants in irradiated oral cancer patients.

In this prospective study, we determined the effects of the time interval between irradiation and implant therapy, implant location, bone-resection surgery, and irradiation dose on implant survival. We analyzed the survival of 446 implants inserted after radiotherapy over a period of up to 14 years in 130 consecutive patients treated for oral cancer. The 10-year overall Kaplan-Meier implant survival percentage is 78%. The difference in survival percentages of implants inserted < 1 year and >/= 1 year after irradiation (76% and 81%, respectively) is not significant. We concluded that implant survival is significantly influenced by the location (maxilla or mandible, 59% and 85%, respectively; p = 0.001), by the incidence of bone-resection surgery in the jaw where the implant was installed (p = 0.04), and by the irradiation dose at the implant site (< 50 Gray or >/= 50 Gray, p = 0.05).

Differences two years after tooth extraction in mandibular bone reduction in patients treated with immediate overdentures or with immediate complete dentures.

In a randomized controlled clinical trial, 74 patients who required immediate dentures were randomly treated with immediate overdentures on two lower canines or with immediate complete dentures. Mandibular bone reduction was measured by use of oblique lateral cephalometric radiographs made at baseline and the results compared with those of one year and two years after denture treatment. Analysis of the data showed that the average bone reduction in the lower canine regions in the first year was 0.9 mm in the immediate-overdenture group and 1.8 mm in the immediate complete-denture group. In the posterior parts of the mandible, the bone reductions were, respectively, 0.7 mm and 1.9 mm. The differences were statistically significant in all measured regions. During the second year, no significant differences in bone reduction were found. The sums of differences in the first two years were significant in all regions except the molar region, preserving the initial difference. Retention of roots of canines beneath a mandibular denture in immediate denture patients, even when they were in poor condition, reduced the collapse of the alveolar processes in all regions of the mandible.

An eight-year follow-up to a randomized clinical trial of participant satisfaction with three types of mandibular implant-retained overdentures.

Studies have shown that mandibular implant overdentures significantly increase satisfaction and quality of life of edentulous elders. Improved chewing ability appears to have a positive impact on nutritional state. Therefore, it is important to determine the best design of this prosthesis over the long term. In this randomized controlled trial, three groups of edentulous participants with atrophic mandibles wore 3 types of implant overdentures. During an eight-year follow-up, only seven of the 110 participants had dropped out of this study. Almost all participants were still satisfied with their overdentures. Participant satisfaction concerning retention and stability of the mandibular overdenture had decreased significantly in the two-implant ball attachment group, whereas the opinion of participants in the single- and triple-bar groups was still at the same level. The long-term results suggest that a mandibular overdenture retained by 2 implants with a single bar may be the best treatment strategy for edentulous people with atrophic ridges.

The state of dentition in relation to nutrition in elderly Europeans in the SENECA Study of 1993.

OBJECTIVE: To analyse the state of dentition and related aspects and to study their influence on the dietary intake of nutrients. DESIGN AND SUBJECTS: In the second cross-sectional measurement of SENECA's follow-up study, 12 research towns in 10 European countries and one town in Connecticut (USA) participated, involving 1424 elderly men and women born between 1913 and 1918. Dentition-related data were obtained from a general questionnaire; nutritional data were collected using a standardized modified dietary history. RESULTS: A large variation in the dental state existed among the towns. Women were more often edentulous and had fewer teeth. Self-reported chewing difficulties varied enormously. Most complaints were found in: women, edentulous subjects without dentures and in the towns in Spain, Portugal and Poland. More dentate women reported having visited their dentist. In the edentulous groups, differences between towns were small; for the dentate groups the percentage of dental visits varied from 0 in Coimbra (Portugal) to 96 in Mansfield (Connecticut/USA). For the edentulous subjects without any prosthetic supply, intakes of carbohydrate and vitamin B6 were significantly reduced. Also intakes of vitamin B1, vitamin C, dietary fibre, calcium and iron tended to be lower in this group. Town-dentition interactions existed for most nutrients. CONCLUSIONS: Substantial differences existed between towns in the influence of dentition on dietary intake.

Osseointegrated oral implants in head and neck cancer patients.

After cancer treatment in the head and neck area, mastication and speech are often affected. Some of the problems encountered can be solved by adequate dental rehabilitation. However, dental rehabilitation is often compromised for various reasons. The change in anatomy due to surgery often results in lack of denture-bearing mucosa. The effects of radiotherapy on the salivary glands and the mucosa result in dry oral tissue and diminished retention of removable dentures. Osseointegrated oral implants can help to solve these problems. Although implant treatment for patients with cancer of the head and neck is covered by the Dutch national health insurance, and there is therefore no financial obstacle, implants have not, so far, been widely used with these patients. In order to establish the possible reasons for this, an analysis was performed. Retrospective data on 95 consecutive patients were collected from records. The indication for the use of oral osseointegrated implants was reviewed. Analysis of the data showed that 45% did not need specific prosthetic rehabilitation. An indication for the use of osseointegrated implants was found in 25% of the patients. For various reasons, only 3% actually received implants. In striving to completely rehabilitate a cancer patient, the possible use of osseointegrated oral implants should be evaluated before the initial oncological treatment begins. The insertion of implants during the initial surgical procedure should be considered more often, with a view to reducing the number of surgical procedures.

The future of extra-oral implantology.

In this paper conclusions are drawn from the experiences of subjects presented in the previous studies in this issue. Indications for bone-anchored implants, the percutaneous passage, implant placement in irradiated tissues, and the psychosocial aspects of treatment are discussed in detail. The future of the extra-oral implantology is also discussed. There is some experience with using bone-anchored implants extra-orally, but both medical and dental staff and the patients themselves are reluctant to use them. In the future, this might change when the percutaneous passage is improved, when hyperbaric oxygen therapy is generally used, when there is more insight into all the possibilities and limitations of bone-anchored devices, and when their application is generally accepted.

Procedure for fabrication of an implant-supported auricular prosthesis.

The procedure for fabrication of an implant-supported auricular prosthesis is described. Treatment is started during the preparatory phase of the surgical procedure because a favorable position of the implants for the epithesis must be chosen at that stage. The fabrication of an epithesis requires close collaboration among the prosthodontist, the maxillofacial technician, and the patient. First, a suprastructure is fabricated on the implants. It consists mostly of rings and a bar connecting the implants. The base of the epithesis consists of hard acrylic resin, which contains clips that provide the retention for the epithesis. The epithesis itself consists of silicone rubber. Great care must be taken in shaping and coloring the epithesis.

Facial disfigurement after cancer resection: a problem with an extra dimension.

Treatment of patients with maxillofacial defects includes not only the technical procedures involved in producing a prosthesis, but also the psychosocial aspects. In all cases, these patients must learn to live with a severe facial disfigurement. People born with congenital defects grow up with disfigurement. For cancer patients, in addition to the mutilation, fear of the tumor plays a significant role. This paper reports on research into this specific treatment aspect. Such patients first must learn to cope with the possibility of premature death. They then must learn to accept facial disfigurement and the fact that society will respond differently to them.

Overdentures supported by ITI implants: a 6.5-year evaluation of patient satisfaction and prosthetic aftercare.

This study reviews the long-term outcome of overdenture treatment in 64 completely edentulous patients who received 218 one-stage ITI implants during the period 1982 until 1988. The evaluation time averaged a period of 80 months, ranging from 66 to 119 months. The results indicate that no implants were lost during this period and that a minimum of surgical and prosthetic treatment was necessary to maintain the overdentures. Patient satisfaction was high and had not significantly changed in comparison with an earlier study on the same group of patients after a mean period of 18 months. The assumption that there would be significantly more complaints about retention of the maxillary denture is not affirmed by this study.

Patient satisfaction with overdentures supported by one-stage TPS implants.

Sixty-four edentulous patients with severe conventional denture problems who had been treated with 218 one-stage titanium plasma sprayed (TPS) screw implants and new overdentures were clinically evaluated and questioned on their experiences with treatment up to 6 years after implant insertion. The results demonstrated that only seven of the implants had failed during this period, resulting in a success rate of 97%. Most of the patients (95%) were satisfied with their new overdentures, and almost all patients (98%) found that their new dentures fit comfortably. Only 3% of the patients treated would not recommend that others undergo similar treatment.

Anatomic consideration for preventive implantation.

The aim of preventive implant therapy is to prevent or delay loss of alveolar ridge bone mass. For use in an anatomic study of 60 mandibles, resorption of the alveolar ridge was classified into four preventive stages: (1) after extraction of teeth; (2) after initial resorption; (3) when the ridge has atrophied to a knife-edge shape; and (4) when only basal bone remains. Implantation in stage 3 necessitates removal of the knife-edge ridge to create space for cylindrical implants. Therefore, implantation in stage 2 is advocated to prevent the development of stage 3. The aim of implantation in stage 4 is to prevent total loss of function of the atrophic mandible.

Denture satisfaction in a comparative study of implant-retained mandibular overdentures: a randomized clinical trial.

This study compared the experiences with surgical procedures and treatment effects of a mainly implant-supported overdenture retained by a transmandibular implant with those of an implant tissue-supported overdenture retained by two cylindrical endosseous implants. Treatment had been assigned according to a balanced allocation method to 95 patients, including a control group who received only conventional complete dentures. Since some of the patients refused the allocated treatment, the "intention to treat" analysis was applied. The results show that the experiences with surgical procedures were significantly more positive for the transmandibular implant group than the endosseous implant group. The differences with respect to satisfaction, complaints, and subjective chewing ability were not statistically significant. These results were unexpected because the overdentures retained by the transmandibular implants were, to a much larger extent, supported by the implant than were the overdentures retained by two endosseous implants.

The cost of dental implants as compared to that of conventional strategies.

The effectiveness of dental implants is widely studied, especially in terms of their clinical outcomes. However, from the policymaker's point of view, variables other than safety and efficacy, such as the costs and effectiveness of dental implants as compared to other treatment alternatives, are vital in decision making. This paper compares the costs of different treatment strategies in a randomized clinical trial in patients with resorbed mandibles and persistent problems with their conventional dentures: treatment with a mandibular overdenture on permucosal dental implants, an overdenture on a transmandibular implant, new dentures after preprosthetic surgery, and new dentures only. Data were gathered on an individual patient level to gain insight into specific cost episodes. Direct costs were subdivided into labor, material, technique, and overhead. Data concerning these components were gathered during the consecutive treatment phases in the first year. Results show that the resources used to treat a patient with an overdenture supported by a transmandibular implant are seven times those of a complete new set of dentures. Comparison of the cost ratio of an implant-retained overdenture supported by permucosal implants and conventional new prostheses proves less unfavorable: 1:3. New dentures after preprosthetic surgery are almost as expensive as treatment with permucosal implants.